By Rail
There is one railway connecting Western Australia with the eastern states. The Indian Pacific (http://www.gsr.com.au) train service runs between Sydney and Perth via Kalgoorlie, Adelaide and Broken Hill. Prices are generally more expensive than air travel, but you can put your car on the train. The train ride is a unique experience in itself, as it can take 3 nights to get to Sydney at the other end of the line and you see a lot of rugged beauty along the way.
By plane
Perth has the only airport in Western Australia with regular international flights.
The vast majority of interstate flights also land in Perth. However there are a small number of interstate flights to Kalgoorlie, Kununurra, Karratha and Broome. Skywest has a weekly flight from Kalgoorlie to Melbourne, however it may still be cheaper to fly Kalgoorlie - Perth - Melbourne depending on the travel dates desired.
The price of flights from other Australian capital cities to Perth fluctuates wildly. The red-eye overnight flights can often be obtained at a discount over the more civilised flight times.
By car
Considering the huge distances, driving into Western Australia from anywhere else is an experience by itself.
There are only two sealed roads into Western Australia: in the south, the Eyre Highway is the most direct route from Adelaide to Perth. In the north, the Victoria Highway connects the Kimberley region with the Northern Territory up to Darwin. Both involve extremely long drives. Perth-Adelaide is at least 3 days of driving with stops only to sleep, and much of the drive is across the extraordinarily barren Nullabor Plain. Darwin-Perth is at least a week.
It is often possible to organise one-way car hire without additional fees from Adelaide to Perth. Shop around, and check conditions carefully, as some cars hired in Adelaide cannot even be driven into Western Australia.
The unsealed Great Central Road, Tanami Track and Gunbarrel Highway run between the Northern Territory and remote Western Australian towns.
Quarantine
There are quarantine rules (http://www.agric.wa.gov.a...) if you are coming from other states in Australia. You cannot bring fruits and vegetables including seeds and cuttings into Western Australia. Frozen fresh food is also not allowed but you will be OK with commercially packaged foods, except honey and bee products. There are quarantine checkpoints set up on the state borders and rules are strictly enforced.. Inspectors board trains into the state to check passengers, and there are checkpoints at all airports.
If you are arriving directly from overseas, additional quarantine rules apply. See the Australia article for details.